Column of adjustable length



June 3, 1969 N. DRNER ET AL COLUMN OF ADJUSTABLE LENGTH Filed sept. 19. 196e Fig.1

sheet @f2 June 3, 1969 N DRNER ET AL 3,447,645

COLUMN OF ADJUSTABLE LENGTH Filed sept. 19. 196e sheet Z of 2 United States Patent O U.S. Cl. 18S-96 6 Claims ABSTRACT F THE DISCLOSURE A column of adjustable length for use as a furniture leg including a cylinder and a piston whose rod projects axially upward from the cylinder. The cylinder portion under Vthe piston is divided by a floating piston. A duct extending through the piston and a portion of the piston rod to a radial bore in the latter is controlled by a valve whose actuating rod extends out of the cylinder through the piston rod. A liquid fills the compartments on either side of the piston, and a compressed gas is contained under the iioating piston.

This invention relates to structural supporting elements whose length may be adjusted continuously, and which may be secured against length change in the adjusted position, and particularly `to columns of adjustable length which Imay be used, for example, as legs in tables of adjustable height and in similar pieces of furniture.

It is known to provide such columns with a cylinder member and with a piston member axially movable in the cylinder member and dividing the cylinder cavity into two compartments. When the available space of the cavity is filled with a iiuid, relative movement of the piston and cylinder members is normally limited by the compressibility of the fluid, and the piston member may be moved in the cylinder cavity beyond these limits only when a by-pass connecting to ythe `two compartments is opened. When a table top is connected to the piston member by a piston rod extending outward `of the cylinder cavity, and the cylinder member is supported on a floor or otherwise, the height of fthe table `top may be adjusted when the by-pass is open, and is substantially fixed when the by-pass is closed.

The object of the invention is the provision of an adjustable column of the type described above which is particularly simple `and rugged so that it is capable of long useful service even under severe operating conditions. Other objects and many of the attendant advantages of -this invention will become apparent to those skilled in the art as the invention becomes better understood bv reference to the fol-lowing detailed `description of preferred embodiments when considered in connection with the accompanyin g drawings in which:

FIG. 1 shows a column of the invention in elevational section on its axis, the column being contracted to its condition of minimum length; and

FIGS. 2 and 3 illustrate modifications of the column of FIG. l in corresponding views.

Referring to the drawing in detail, and initially to FIG. l, there is seen an upright cylinder whose bottom is sealed by an imperforate fixedly inserted, cup-shaped closure member 12. The 'top of the cylinder cavity 90 is bounded by a closure assembly 14 mainly consisting of an annular plug 16 which is prevented from axial move- 3,447,645 Patented June 3, 1969 ICC ment outward of the cylinder by yan internal flange 26 on the latter, a retaining ring 18 labuttingly engaging the ange, :and an annular gasket 24 axially interposed between the plug 16 and the ring 18. The plug 16 sealingly engages the inner lwall of the cylinder 10 and has a `axial aperture in which a guide bushing 20 is sea-led tothe plug 16 by a gasket 22.

A tubular piston rod 28 is axially guided in the aperture of -the plug 16 by the bushing 20 and is sealed to the plug by Ethe gasket 22. The lower or inner end portion 30 of the rod 28 has a shoulder 46 against which a radial face of a piston 32 is held by an internally threaded cap 44 mounted on the threaded terminal p-art of the piston rod portion 30. The piston 32, which is equipped with a circumferential sealing ring 34, `axially divides the cylinder cavity into first and second compartments 90b and 90a near the closure Vmember 12 and the closure assembly 14 respectively. The cap 44 also retains an apertured plug 42 in the downwardly directed orifice 40 of the axial bore 36 in the piston rod 28. The axial aperture 58 of the plug 42 is aligned with an opening 60 in the cap 44. Threads 70 4on the upper end portion of the piston rod 28 which projects from `the cylinder 10 secure a connector 68 to the piston rod. The connector is normally attached to a table top or the like while the closure member 12 may stand on the floor.

The top face 56 of the plug 42 provides a recessed conical seat about the aperture 58 for a correspondingly conical valve member 54 mounted on a valve stem 52. The valve stem is cylindrical and of smaller diameter than `the duct portion 92 of the bore 36 in which it is arranged `so as to leave an unobstructed passage 93 of annular cross section in the duct 92, the passage being bounded in a radially outward direction by the cylindrical inner wall 38 of `the piston rod 28 in the bore 36. When the valve member 54 is lifted from its seat 56, `a bV-pass connection is opened between the compartments 98a, 90b through a radial bore or conduit 62 extending in the piston rod 28 between the passage 93 and the radially aligned portion of the compartment 90a, the passage 3, the aperture 58, and the opening 60.

The valve member 54 is normally pressed against the seat 56 by a stepped, cylindrical valve actuating rod 48, coaxially fastened to the stem 52, and having a main portion 50 of greater diameter than that of the stem 52. The rod portion 50 is sealed to the piston rod by an annular seal 64 held in position at the ytop end of the piston rod 28 by a retaining washer 66 interposed between the pist-on rod and the connector 68. The outermost portion 74 of the valve kactuating rod 48 is of reduced cross `section so las to define a shoulder 78 of the rod 48 which carries a Washer 80. Another Washer 86 is retained in an axial bore 72 of the connector 68 by a spring c-lip 88. The washers 80, 86 provide abutments for cup springs 82 which normally press the valve actuating rod 48 inward of the cylinder 10. A non-illustrated knob attached to the valve actuating rod 48 by ythreads 76 permits the valve member 54 to be lifted from the valve seat 56 against the restraint of the cup springs 82.

The compartments 90a, 90b and the ducts and passages which connect the compartments when the valve member 54 is lifted from its seat 56 are filled with compressed air or another gas, such yas nitrogen, under a pressu-re normally higher than atmospheric pressure and selected for the load to be supported by the column, and for the permissible sag of the column Iunder load. The 4sag is inversely rela-ted to the compressibility of the fluid in the cylinder cavity, and may be reduced to an insignificant value by filling the cylinder cavity with a suitable liquid. The filling nipple, normally sealed, which permits the cylinder cavity 90 to be filled or replenished with fluid in an obvious manner is not shown in the drawing.

It it is desired to adjust the column to a length greater than that shown, the valve actuating rod 48 is pulled upward by the knob (not shown) on the threaded top portion 74, and lthe connector 68 and lcylinder 10 are shifted axially relative to each other as desired. The adjusted position is secured by releasing the rod 48, except for the lpredictable sag due 'to the resilience of rthe fluid in the cylinder `10.

The column ci the invention illustrated in FIG. 2 is closely similar in many features to that shown in FIG. 1, and reference numerals differing from those of FIG. 1 by the addition of 200 designate structural and functional equivalents of the corresponding features in FIG. l.

The cavity 290 of the cylinder 210 is axially bounded by closures 212, 214, the latter including a plug 216, a retaining ring 218, a guide bushing 220, and annular gaskets 222, 224 retained #by a ange 226. A tubular piston rod 228 has an axial bore 236 and an internal cylindrical wall 238 in the bore. The inner or lower end portion 230 of the rod 228 carries a piston 314 which consists of two circular metal discs 316, 318 and an axially interposed rubber ldisc 320 which seals the piston to the cylinder 210. The piston 314 is held against a shoulder 246 of the piston rod 228 by a cap 244 which abuts against the lower radial face ofthe piston.

A by-pass which connects the two compartments 290a, 290b of the cylinder cavity 290 above and below the piston 314 includes a radial bore or conduit 262 in the piston rod portion 230 and is controlled by a valve arrangement operated by an elongated actuating rod 248 movable in the bore 236 ofthe piston rod 228, and sealed to the piston rod by a resilient ring 264 held in position by a retaining washer 266 clamped between the upper end of the piston rod and a connector 268. The portion 250 of the cylindrical valve actuating rod 248 in the cylinder 210 has the t same diameter as the outer portion 322 which upwardly projects from the cylinder.

The column shown in FIG. 2 differs from that described with reference to FIG. 1 mainly by details of the valve arrangement. The actuating rod 248 carries a coaxial, cylindrical valve stem 300 integral with a valve member 302 which extends outward through an opening of the cap 244. A disc-shaped abutment 312 oi relatively rigid metallic material is mounted on the valve member 302 in the cavity compartment 290b and normally engages an external face ott the cap 244, as is seen in FIG. 2. An upwardly tapering conical face 304 of the valve member 302 conformingly engages a valve seat 306 in the central opening of a iiat sealing ring 308 which is held in position between the bottom oriiice of the piston rod 228 and the cap 244 by an annular backing plate 310.

The weight of a table top or other supported structure attached to the connector 268 causes increased fluid prssure in the compartment 290b to hold the valve member 302 in its seat 306. Damage to the resilient seat is prevented by engagement of the much more rigid abutment disc 312 with the equally rigid cap 244. If it is desired to vary the length of the column, the outer actuating rod portion 322 is depressed until iluid may iiow between the compartments 2900:, 290b as needed. The valve may then be closed by upwardly pulling the rod portion 322, but the valve normally closes automatically when an applied load initially causes liquid to iiow upward from the compartment 29011 into the compartment 290e under the pressure applied by the piston 314.

FIG. 3 shows -a further modification of the column of FIG. 1 which is preferred when the compartments 190a, 19011 above and below the piston 132 are filled with liquid. Execpt for dimensional relationships, and the features to be discussed in more detail hereinafter, the column illustrated in FIG. 3 is identical in structure and -function with. that discussed above with reference to FIG. 1, and corresponding elements have been provided with the same reference numerals preceded by the FIGURE l. They do not require further description.

CII

The compartment 190b between the piston 132 and the bottom closure 112 is axially partitioned by a floating piston 196. The part 194 of the compartment near the bottom closure 112 is iilled with compressed air and is hermetically sealed from the remainder of the compartment 1901: by a circumferential sealing ring 198 on the oating piston lor partition 196. The compartment 190e, t-he duct 192 in the piston rod 148, and the part of the compartment 190b remote from the bottom closure 112 are illed with a liquid, for example, hydraulic brake iluid of the common automotive type. The compressed gas in the compartment part or chamber 194 expands and contracts when the piston rod 130 moves outward and inward of the cylinder during length adjustment, thus permitting the use of a liquid of very low vapor pressure in all other portions of the cylinder cavity which is not practical in the devices shown in FIGS. 1 and 2.

The apparatus illustrated in FIG. 3 is operated as described above with reference to FIG. 1.

What is claimed is:

1. A column of adjustable effective length comprising, -in combination:

(a) a cylinder member having an axis and defining an axially extending cavity therein;

(b) rst closure means including an imperforate closure member tixedly fastened to said cylinder member in sealing engagement and axially closing one end of said cavity;

(c) second closure means axially spaced from said iirst closure means in sealing engagement with said cylinder member and axially bounding the other end of said cavity, said second closure means being formed with an axial aperture therethrough;

(d) a piston member in axially movable sealing engagement with said cylinder member in said cavity, said piston member separating irst and second compartments ot said cavity respectively adjacent the corresponding closure means;

(e) a piston rod member having an inner portion fastened to said piston member and an outer portion sealingly passing through said yaperture outward of said cavity,

(1) said inner portion of said piston rod member dening an axial duct therein, a first axial portion ot said duct having :an orice communieating with said iirst compartment, and a second axial portion of said duct being radially aligned with said second compartment,

(2) said piston rod member being formed with a radial conduit connecting said duct with said second compartment;

(f) valve means or opening and closing said duct, said valve means including a valve seat, a valve member axially movable toward and away from a position of sealing engagement with said valve seat, a valve stem member axially movable in said piston rod member and fastened to said valve member, tand actuating means at least partly outside said cavity for axially moving said stem member;

(g) partition means defining a chamber, said partition means including a partition member separting said chamber from one of said compartments;

(h) `a liquid substantially filling said compartments Iand said duct;

(i) a `gas under a pressure higher than atmospheric pressure iilling said chamber,

(1) said partition member being movable inward yand outward of said chamber and of said one compartment under the pressures of said liquid :and of said gas,

(2) said inner portion of said piston rod member being formed with a shoulder, said piston member having two radially extending axially spaced opposite faces, one of the -faces abuttingly engaging said shoulder, and said piston rode member having a `free terminal portion projecting from said piston member into said rst compartment;

(j) -a cap member threadedly fastened to said terminal portion and abuttingly engaging the other one of said faces; and

(k) apertured plug means positively retained in said orifice by said cap member, the cap member being formed with an `opening aligned with the aperture of said plug means, a portion of said plug means constituting said valve seat.

2. A columnas set forth in claim 1, wherein said valve member is offset from said valve seat toward said second closure means when said valve means open said duct, the valve means further including yieldably resilient means interprosed between said piston rod member and said vactuating member for urging said valve member against said valve seat.

3. A column as yset forth in claim 1, further comprising connecting means on said outer portion of the piston rod member for securing the piston rod member to structure to be supported by the column.

4. A column as set Vforth in claim 1, wherein said partition member is axially movable in said cavity in sealing engagement with said cylinder member, and said chamber is a portion of said cavity interposed between said partition member and said rst closure means.

5. A column as set forth in claim 1, wherein said valve seat is lannular about said orifice, and said valve stem member taxi-ally extends in said duct, leaving lan unobstructed passage of annular cross section in said duct, said passage connecting said conduit with said orifice.

6. A column as set forth in claim 5, wherein said actuating means include an axially elongated lactuating member means slidable in said piston rod member, and sealed to the same, an inner portion of said actuating member having a cross section greater than the cross section of said stem member 'and being xedly fastened to the same, and an outer -portion of said actuating member outwardly projecting `from said piston rod member.

References Cited UNITED STATES PATENTS 2,042,443 5/ 1936 Buckstone. 2,624,318 1/1953 Walder 92-12 X 3,236,515 2/ 1966 Ackerman.

3,315,768 4/1967 Stuhler et al. 188-67 3,078,967 2/ 1963 lBrown et al. 188-96 FOREIGN PATENTS 286,626 2/ 1965 Netherlands.

GEORGE E. A. HALVOSA, Primary Examiner.

U.S. Cl. X.R. 18S- 67; 248-354 

